Identifying possible target of action of 4,4a-dihydroxanthones in bacterial cells

Abstract

Introduction. Partially hydrogenated derivatives of xanthone, dihydroxanthones, are being intensively studied. They are of interest due to their antimicrobial, antitumor, and antioxidant effects. Many researches are focused on the study of the cytotoxicity of dihydroxanthones and very little information is available on their antimicrobial activity. Therefore, the study of the antimicrobial activity and mechanism of action of new synthetic derivatives of 4,4a-dihydroxanthone is relevant. Preliminary studies have demonstrated that 4,4a-dihydroxanthones are active against gram-positive bacteria and have a pronounced anti-staphylococcal effect. Namely, 5-bromo-4,4-dimethyl-7-chloro-4,4a-dihydroxanthone (BDC-DX) was shown to be the most active derivative.Aim of the study was to determine the possible target of action of the active derivative of BDC-DX in bacterial cells and its acute toxicity.Materials and methods. The method of measuring the intensity of absorption of the crystal violet dye by bacteria cells was used to prove the effect of BDC-DX on the permeability of the cytoplasmic membrane in bacterial cells. The plasma coagulase activity of Staphylococcus aureus was tested under the action of dihydroxanthone to determine the effect of dihydroxanthone on the process of protein synthesis. Plasmid DNA digestion method was used to study the effect of the compound on bacterial DNA. The acute toxicity of BDC-DX was determined by the express method of V.B. Prozorovsky.Results and discussion. BDC-DX increased the permeability of the cytoplasmic membrane of S. aureus. Dihydroxanthone did not directly affect the plasma coagulase activity of Staphylococcus and showed a weak damaging effect on bacterial DNA. The compound induced breaks in plasmid DNA at a very high concentration — 1 mM or 384 pg/ml and higher. BDC-DX is a low-toxic compound (the average lethal dose for oral administration of the compound is 1710 ± 170 mg/kg, the average lethal dose for intraperitoneal administration of the compound is 116.9 ± 13.3 mg/kg).Conclusion. For the first time, in-depth study of the possible mechanism of action of a new synthetic biologically active compound from the group of 4,4a- dihydroxanthones, BDC-DX, was conducted. A likely target of 5-bromo-4,4-dimethyl-7-chloro-4,4a-dihydroxanthone in S. aureus cells is the cytoplasmic membrane. BDC-DX did not affect the process of protein synthesis, namely the activity of the plasma coagulase enzyme. The compound had no pronounced damaging effect on bacterial DNA. It was found that 4,4a-dihydroxanthone refers to low-toxic compounds.